(a) Make a labelled diagram of the vertical section of the mammalian tooth.
(b) Describe the role of the following in mammalian nutrition: (i) teeth; (ii) tongue ; (iii) saliva; (iv) stomach .
(c) Describe how to test for protein in a food sample
Explanation
(a)
(b)(i) The role of teeth in nutrition are:
(1) For chewing, mastication, cutting, grinding and biting of foods
(2) For tearing and breaking Enamel food into particles
(3) Exposing large surface area for functioning or action of the enzymes.
(ii) Role of tongue in nutrition are:
(1) movement of food in the Neck buccal cavity or mouth
(2) it allows the mixing of food with Cement saliva or enzyme
(3) It assists in swallowing or pushing of bolus into the gullet
(4) enables the formation of food into bolus.
(iii) Role of saliva in nutrition are:
(1) For lubrication of food
(2) it allows for easy chewing or movement of food in the mouth, for swallowing.
(3) Acts as a solvent for food
(4) Contains ptyalim or enzyme for digesting cooked starch
(5) It is slightly alkaline.
(iv) The role of stomach in nutrition are:
(1) production of gastric juice which contains pepsin for protein digestion
(2) The juice contains Renin for coagulation of liquid protein or milk. The stomach also has hydrochloric acid to form acid medium which kills bacteria. It helps in storing or temporal storage of undigested food.
(3) It produces churning movement which aids mixing of food with digestive juice.
(c) Test for protein can be carried out through million's test or biuret test.
Million test: Prepare an aqueous suspension of food sample, add a few drops of million's reagent. White precipitate is formed. Then, heat the mixture. Red or pin red precipitate is formed, which shows the presence of protein.
Biuret Test:- Make an aqueous suspension of food sample, add 2cm3 of 2% of sodium hydroxide solution, mix or shake it. Add a few drops of 1% dilute copper sulphate solution. Violet or purple colour will be formed which shows the presence of protein.